Chapter 11: Root Morphology

Root pain due to exposed dentin is caused by gingival recession. Exposed spots of dentin can stimulate pulpal nerves through the cementoenamel junction (CEJ).

• Both statements are true.

• The first statement is true, the second is false.

• The first statement is false, the second is true.

• Both statements are false.

Answer explanation

P. 105 The dentin that surrounds the pulpal tissue of the root is itself covered by an imperfect layer of cementum. This patchwork of cementum has bare areas where dentin is exposed. If the tooth root is exposed because periodontal disease, recession, trauma, or any form of pathology, these exposed spots of dentin can stimulate the pulp nerves through their tubules.

Pressure and temperature responses are elicited by all of the following EXCEPT one. Which one is the EXCEPTION?

• Bone

• Periodontal ligament

• Gingiva

• Pulp tissue

Answer explanation

P. 105 Pressure and temperature responses are not elicited by pulpal tissue. Instead the nerve tissue within bone, gums (gingiva), and the periodontal ligament elicits these responses.

Blood vessels traveling through the apical foramen support nerves and odontoblasts because the blood supply enables delivery of essential nutrients as well as removal of harmful products.

• Both the statement and the reason are correct and related.

• Both the statement and the reason are correct but are NOT related.

• The statement is correct, but the reason is NOT correct.

• The statement is NOT correct, but the reason is correct.

• NEITHER the statement NOR the reason is correct.

Answer explanation

P. 105 These vessels enter and exit through a orifice in the apex of the root called the apical foramen. They also provide a system to remove harmful products and carbon dioxide from the tooth.

Each of the following teeth frequently has two roots EXCEPT one. Which one is the EXCEPTION?

• Maxillary first premolar

• Maxillary second premolar

• Mandibular first molar

• Mandibular second molar

Answer explanation

Maxillary first premolar has 2 roots.

Maxillary second premolar has 1 root.

Mandibular first molar has 2 roots.

Mandibular second molar has 2 roots.

Maxillary molar root trifurcations are located on each of the following surfaces EXCEPT one. Which one is the EXCEPTION?

• mesial

• distal

• lingual

• buccal

Answer explanation

p. 107 The three different furcation areas for maxillary molars between the two buccal roots between distobuccal and mesiobuccal. Basically meaning located mesial, distal, and buccal.

Orthodontics requires a sustained pressure to move teeth to a new location. Osteoblasts respond to the new location by forming new bone.

• Both statements are true.

• The first statement is true; the second is false.

• The first statement is false; the second is true.

• Both statements are false.

Answer explanation

P. 106 - 107 On the opposite side of the tooth the PDL is tensed to accommodate the tooth's movement. This tension is exerted on bone. Osteoblastic bone-forming cells respond to the tension by forming new bone. In this way,responding to pressure and tension, the bone is remodeled. The net result is that the tooth moves away from the external force into a new location.

Teeth with curved roots afford resistance to apical and distal forces but are vulnerable to occlusal forces. Roots with triangular cross section are particularly vulnerable to lateral displacement.

• Both statements are true.

• The first statement is true, the second is false.

• The first statement is false, the second is true.

• Both statements are false.

Answer explanation

P. 106 Curved roots → resistance to occlusal, apical and distal forces

The direction of the root tip can even offer resistance to movement. Most single-rooted teeth have their root tips pointed distally. This distal slant offers slightly more resistance to movement compared with a straight vertical upright shape.

Root canal therapy in third molars is considered very unpredictable because the tooth is located so far distally in the mouth.

• Both the statement and the reason are correct and related.

• Both the statement and the reason are correct but are NOT related.

• The statement is correct, but the reason is NOT correct.

• The statement is NOT correct, but the reason is correct.

• NEITHER the statement NOR the reason is correct.

Answer explanation

P. 108 Mandibular third molars can have one, two, or more root canals. because third molar roots are usually curved, their root canals are very unpredictable.

Mandibular premolars typically have two pulp canals. Maxillary first premolars are more likely than maxillary second premolars to have two pulp canals.

• Both statements are true.

• The first statement is true, the second is false.

• The first statement is false, the second is true.

• Both statements are false.

Answer explanation

P. 108 Mandibular premolars usually have one canal. Maxillary premolars often have two canals. The maxillary first premolar is more likely to have two canals and even two roots compared with the maxillary second premolar.

During hypercementosis, excess cementum is deposited

• Along the CEJ

• Irregularly, throughout the root surface

• At the dentinocemental junction

• At the apex of the root

Answer explanation

P. 105 The apical third of the root at or near its apex can continue to form cementum on the outside of the root. If this process is extreme, it is called hypercementosis, and it forms a cementoma at the apex of the root.